Wood stains and method of preparing



United States Patent WOOD STAINS AND NIETHOD OF PREPARING Leo J. Noyak,Dayton, Ohio, assignor to Commonwealth Engineering Company of Ohio,Dayton, Ohio No Drawing. Application June 25, 1956 Serial No. 593,384

3 Claims. (31. 8-6.5)

This invention relates to staining compositions and more particularly toa composition for staining wood, paper and the like cellulose containingsubstances and to a method of producing the same.

Briefly, the invention provides a brown colored stain as prepared fromdiazonium salts such as benzenediazonium chloride. The stainingcomposition comprises an alkaline degradation product made fromdiazotized aniline or the like amine, the resultant brown coloredsubstance which is extracted with a petroleum is fast to light and hasbeen found to be especially useful for staining wood surfaces.

It is an object of the invention to provide a staining solutioncomprising the degradation products of benzenediazonium salts as thecoloring or staining agent. Useful staining compositions are providedwhich are non-grain raising and fast to light by dissolving ordispersing suitable quantities of the brown colored, diazotate asextracted in organic solvents such as toluol, xylol, solvent naphtha andlow carbon chain aliphatic alcohols such as methanol, ethanol, etc., orsuitable mixtures of these organic solvents, the petroleum solventsbeing preferred because of their higher solvent power.

The wood stains of the prior art may be looked upon as of three types,first, the water type, second, the oil type, and third the spirit type.The water stains generally consist of aqueous solutions of aniline dyes,which are applied in any desired manner, as by brushing to the woodsurface to be stained. The dye in such water stains is in a form that isnon-bleeding and non-fading, but these Water stains have certainobjectionable characteristics. For example, such water stains have thevery highly undesirable effect of raising the grain. The surface mustthen be sanded, but because of the grain-raising efiect of the waterstain, a thin shellac coating must be applied to the stained wood inorder to stiffen the fibers in order that they may be uniformly sanded.When an open grained wood is used, it is necessary after the sandingoperation to apply a filler to the surface over which the varnish orlacquer is applied. The grain-raising efiect of the water stainsseriously militates against their effectiveness. Furthermore the waterstains have indifferent penetration, the dye remaining substantially onthe top surface of the wood instead of impregnating the fibers.

The oil stains have the desirable property of penetrating into the woodsurface, but they are open to several material objections. Owing to thepreliminary treatment given the dyes to render them available in the oilstain compositions, the resultant product is not light fast, and it isalso subject to the so-called bleeding effect. Furthermore any excess offatty acid present in such compositions affects the practicability andthe durability of the surface finish, producing such effects as retardeddrying and as checking.

The spirit stains, which utilize aniline dye bases so treated as to besoluble in alcohol, are not used very extensively because they are alsosubject to a number of undesirable qualities, such as lack ofpenetration into the ice wood surface, and lack of permanency of colorand fading qualities similar to those of the oil-type stains. The spiritstains are also subject to the bleeding effect, and in many instancesalso give rise to grain raising.

Among the objects and advantages of the present invention is theproduction of wood stains which shall have the property of penetratingthe wood surface to which they are applied without producing anysubstantial grain raising, and which at the same time will not exhibitthe fading and bleeding properties of the prior art stains.

Other objects and advantages will appear from the more detaileddescription set forth below, it being understood however that this moredetailed description is given by way of illustration only, and not byway of limitation.

The invention will be more fully understood by the following specificexamples:

Example I Aniline is diazotized with sodium nitrite and hydrochloricacid while retained at a temperature of about 5 C. using an ice bath.The aniline is dissolved in water containing approximately threeequivalents of hydrochloric acid. While the solution is held at atemperature of 0 to 5 C., an aqueous solution of sodium nitrite is addedin small portions until the solution, as shown by starch-iodineindicator comprises excess nitrous acid and forming a benzenediazoniumchloride solution.

The resultant benzenediazonium solution cooled to about 10-20" C. ispoured into a strong sodium hydroxide solution (aqueous solutioncontaining 10-30% by weight sodium hydroxide), the alkali being presentin excess of that required to form the sodium salt to decompose thebenzenediazonium chloride to form the desired product. The solution isthenacidified with hydrochloric acid and the brown product is extractedwith toluene to provide a staining composition. Preferably the productformed by acidification is neutralized or at least partially so, the pHbeing in the range of about 4 to 6.5 prior to extracting. This may bedone by carefully introducing the hydrochloric acid so that excess acidis avoided.

The brown colored product or dye, although not definitely knownchemically, appears to be sodium isodiazotate with a minor proportionateamount (5-20% by weight) of benzenenitrosoamine. In general the greaterthe acidity the more benzenenitrosoamine present. A 20-30% solution ofthe brown colored sodium' isodiazotate in petroleum solvent makes asuitable staining composition.

Example 11 Ten grams of aniline and twenty grams of concentratedhydrochloric acid (40% HCl) are dissolved in grams of distilled or tapwater. The solution is thereafter cooled to O5 C. and there is addedslowly with stirring a solution of 10 grams sodium nitrite in 30 cc. ofwater, at a temperature of 0 to 5 C. The temperature should not beallowed to rise above about 10 C. The resulting solution ofbenzenediazonium chloride is then poured slowly with stirring intoapproximately cc. of an aqueous solution of sodium hydroxide (30% NaOH).The resultant alkaline solution is then acidified with stronghydrochloric acid until the solution has a pH of about 6.0 and thesolution is allowed to come to room temperature.

The brown colored product is then extracted with toluene to produce thebrown colored staining product.

A concentration containing approximately 30% of the brown coloredextract in the petroleum solvent produces a satisfactory stain for wood.Where a more concentrated stain is desired, the brown colored oilyextract may be increased to the desired proportionate amount in thesolvent.

- 3 Example Ill A dark oily stain product is produced similarly as inExample II utilizing methyl aniline as the amine in producing thediazotized alkaline me'tal brown colored extract. The stain when appliedas a 50% concentration on wood produced a dark brown stain having goodlight fastn'essri r -In preparing the diazotiz ed color product inaccordance with the invention, other alkaline solutions may be utilizedsuch as potassium hydroxide and/ or mixtures of alkaline metalhydroxides. Further, other amines such as the heterocyclic amines may beused to produce different shade colored products for use as a stain.

The alkaline degradation products as are produced form diazotizedaromatic color products which are immiscible with water but are readilysoluble in petroleum solvents such as benzene, xylene, etc., as well asmixtures of the same with lower aliphatic alcohols as aforementioned.The stain provides aproduct which is especially useful for staining woodand a dye which is fast to light. This is shown from tests made whereinwood surfaces stained with the product of this invention are subjectedto prolonged exposure under ultra-violet light for a period of 72 hoursor longer. 7 In the above examples other organic solvents having apetroleum base or mixture thereof with aliphatic alcohols may beus'ed'as the solvent for application of the stain.

It will be understood that while there have been given herein certainspecific examples of how the stain can be produced and utilized in thepractice of this invention, it is not intended thereby to limit theinvention thereto or to the specific materials, proportions orconditions set forth inasmuch as those skilled in the art will readilyappreciate that such details may be varied and substitution made in thepractice of the invention. The same is accordingly understood to comewithin the scope and spirit of this invention and as more particularlyset forth in the appended claims.

What is claimed is:

l. A process for producing a wood stain which com prises the steps ofdiazotizing'aniline with sodium nitrite and hydrochloric acid andneutralizingthe resultant benzenediazonium solution with sodiumhydroxide, acidifying the resultant product, and extracting the browncoloring constituent with toluene to provide a staining compositioncomprising a. mixture of sodium isodiazotate and benzenenitrosoamine,said solution having a pH of between about 4.0 and 6.5.

2. A process for producing a wood staining composition comprisingproviding a diazotized amine solution, alkalizing said solution withalkali metal hydroxide to produce vthe alkali metal salt ofbenzenediazonium 'chloride, acidifying the resultant alkaline solutionof benzeneisodiazotate and recovering the brown colored constituenttherefrom, said brown colored constituent comprising a mixture of alkalimetal isodiazotate and benzenenitrosoamine, and dispersing saidconstituent in an organic solvent vehicle.

3. A brown colored dye solution useful as a wood staining compositionconsisting of a mixture of alkali metal isodiazotate andbenzenenitrosoarnine dissolved in toluol, said benzenenitrosoaminecomprising from 5 to 20% by weight of the mixture.

References Cited in thefile of this patent UNITED STATES PATENTS

1. A PROCESS FOR PRODUCING A WOOD STAIN WHICH COMPRISES THE STEPS OFDIAZOTIZING ANILINE WITH SODIUM NITRITE AND HYDROCHLORIC ACID ANDNEUTRALIZING THE RESULTANT BENZENEDIAZONIUM SOLUTION WITH SODIUMHYDROXIDE, ACIDIFYING THE RESULTANT PRODUCT, AND EXTRACTING THE BROWNCOLORING CONSTITUENT WITH TOLUENE TO PROVIDE A STAINING COMPOSITIONCOMPRISING A MIXTURE OF SODIUM ISODIZOTATE AND BENZENENITROSOAMINE, SAIDSOLUTION HAVING A PH OF BETWEEN ABOUT 4.0 AND 6.5.